Digital logic devices with extremely skewed trip points and reset circuitry for rapidly propagating signal edges

ABSTRACT

The invention includes digital logic devices with extremely skewed trip points and reset circuitry for rapidly propagating signal edges. Embodiments of skewed logic devices in accordance with the present invention include inverters, buffers, NOR gates and NAND gates for rapidly propagating a selected “fast” edge of an input signal. Additional embodiments include pulse stretchers, memory devices, substrates, computer systems and methods incorporating the skewed logic devices of the present invention. Each embodiment of a skewed logic device of the present invention is configured to propagate either a fast rising edge or fast falling edge of an output signal, i.e., the “fast” edge, at rates comparable to those of domino logic. An advantage of the skewed logic devices of the present invention over conventional CMOS logic devices is rapid edge propagation. Additionally, virtually all of the input gate loading is devoted to the fast edge being propagated. Additionally, the reset networks, as disclosed herein, are buffered by at least two gates, thus reducing loading seen by the input or the output of the skewed logic device.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a divisional of application Ser. No.09/922,027, filed Aug. 3, 2001, pending.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to digital logic devices used inintegrated circuits. More specifically, the present invention relates todigital logic gates, such as inverters, buffers, NAND gates and NORgates, with extremely skewed trip points and reset circuitry forpropagating fast signal edges. Additionally, the present inventionrelates to circuits, substrates, systems and methods incorporatingdigital logic gates with extremely skewed trip points.

[0004] 2. State of the Art

[0005] Advances in semiconductor manufacturing technologies have alloweddigital integrated circuit designers to place several milliontransistors interconnected on a single substrate. Concurrently, advancesin computer architecture and particularly processor architecture havedriven ever-shorter cycle times. These advances in semiconductormanufacturing and processor architecture have forced digital integratedcircuit designers to consider new ways of implementing basic circuitfunctions, particularly for low-power and high-speed applications.

[0006] In metal oxide semiconductor (MOS) devices, the speed ofoperation is limited by the resistance of a given MOS transistor drivingthe capacitance (input load) of the next MOS transistor. The outputcurrent of a MOS transistor is proportional to its channel width. Thus,if a narrow channel transistor is used to drive a high capacitance load,a relatively long delay results. To reduce this delay in digitalcircuits, a series of cascaded inverters is frequently used. Forexample, see U.S. Pat. No. 5,343,090, explicitly incorporated herein byreference for all purposes.

[0007] Increasing clock frequency is another approach to reducing cycletimes. However, by increasing clock frequencies, fewer (or shorter)logic gate delays are permitted during each clock cycle. To accommodatethis need for shorter gate delays, a number of circuit technologies havebeen implemented for high-speed operation.

[0008] Static full complementary metal-oxide semiconductor (CMOS) logicprovides two types of transistors, a p-type transistor (PMOS) and ann-type transistor (NMOS). The terms “device” and “structure” used hereinto describe CMOS logic include PMOS and NMOS transistors. FIG. 1illustrates a conventional inverter 100 constructed from CMOS logic.FIG. 2 is a timing diagram for conventional inverter 100 illustratinginput signal IN and output signal OUT. Additionally, input gate loadingis shared between devices that generate rising and falling edges of aconventional CMOS inverter.

[0009] Dynamic logic structures, e.g., domino logic devices, propagatesignal edges much quicker than static full CMOS logic. Domino logicrefers to a circuit arrangement in which there are severalseries-coupled logic stages having precharged output nodes. The outputnode of an individual logic stage is precharged to a first logic level.Logic signals are then applied such that, depending on the logicfunction being implemented and the state of the various input signals,the output node can be switched to a second logic level. As each dominostage in the chain evaluates, the output of the next domino stage may beenabled to switch. However, problems with domino logic include thenecessity for precharge circuitry and charge sharing induced noise.

[0010] There is a need in the art for digital logic devices capable ofpropagating selected signal edges more rapidly than conventional CMOSinverters, with virtually all of the input gate loading (capacitance)devoted to the devices that generate a fast edge being propagated, andwithout the charge sharing induced noise problem associated with dominologic.

SUMMARY OF THE INVENTION

[0011] The invention includes digital logic devices with extremelyskewed trip points and reset circuitry, referred to herein as “skewedlogic devices,” for rapidly propagating signal edges. Embodiments ofskewed logic devices according to the present invention includeinverters, buffers, NAND gates and NOR gates. The invention alsoincludes circuits, substrates, systems and methods including skewedlogic devices as disclosed herein. Each embodiment of a skewed logicdevice of the present invention is configured to rapidly propagateeither a rising edge or falling edge of an output signal, i.e., the“fast” edge, with a delay comparable to that of domino logic. The othercorresponding, “slow” edge propagates with a delay of about 2 to 4ordinary gate delays.

[0012] An advantage of the skewed logic devices of the present inventionover conventional CMOS inverters is rapid edge propagation. Anotheradvantage is that virtually all of the input gate loading is devoted tothe fast edge being propagated. Additionally, the reset networksdescribed herein are buffered by at least 2 gates, thus reducing loadingseen by the input or the output of the skewed logic device associatedwith conventional reset circuitry.

[0013] An embodiment of a skewed inverter rising logic device of thepresent invention for rapidly propagating a rising edge of an outputsignal includes a fast inverter rising having a large p/n channel widthratio for receiving an input signal and rapidly propagating a risingedge onto the output signal in response to receiving a falling edge onthe input signal. A skewed inverter rising logic device further includesa pull-down reset network connected in parallel with the fast inverterrising for resetting the output signal after the rising edge has beenpropagated onto the output signal, and a feedback delay circuitconnected in parallel with the pull-down reset network for delaying andreturning the output signal back to the pull-down reset network.

[0014] An embodiment of a skewed inverter falling logic device of thepresent invention for rapidly propagating a falling edge output signalincludes a fast inverter falling having a large n/p channel width ratiofor receiving an input signal and rapidly propagating a falling edgeonto the output signal in response to receiving a rising edge on theinput signal. Skewed inverter falling logic device further includes apull-up reset network connected in parallel to the fast inverter fallingfor resetting the output signal after the falling edge has beenpropagated onto the output signal, and a feedback delay circuitconnected in parallel with the pull-up reset network for delaying andreturning the output signal to the pull-up reset network.

[0015] An embodiment of a skewed buffer rising logic device of thepresent invention for rapidly propagating a rising edge of an outputsignal includes a fast inverter falling having a large n/p channel widthratio for receiving a rising edge of an input signal and rapidlypropagating a falling edge of an intermediate signal in response theretoand a fast inverter rising having a large p/n channel width ratio and inseries with the fast inverter falling for receiving the rapidlypropagated falling edge of the intermediate signal and rapidlypropagated rising edge on the output signal. A skewed buffer risinglogic device may further include a reset network coupled to the fastinverter falling and the fast inverter rising for resetting outputsignals of the fast inverter falling and the fast inverter rising afterthe rising edge of the output signal has been rapidly propagated, and afeedback delay circuit operably coupled between an output of the fastinverter rising and an input of the reset network for propagating theoutput signal to the reset network.

[0016] An embodiment of a skewed buffer falling logic device of thepresent invention for rapidly propagating a falling edge of an outputsignal includes a fast inverter rising having a large p/n channel widthratio for receiving a falling edge of an input signal and rapidlypropagating a rising edge of an intermediate signal in response theretoand a fast inverter falling having a large n/p channel width ratio andin series with the fast inverter rising for receiving the rapidlypropagated rising edge of the intermediate signal and rapidly propagatedfalling edge on the output signal. A skewed buffer falling logic devicemay further include a reset network coupled to the fast inverter risingand the fast inverter falling for resetting output signals of the fastinverter rising and the fast inverter falling after the falling edge ofan output signal has been rapidly propagated, and a feedback delaycircuit operably coupled between an output of the fast inverter fallingand an input of the reset network for propagating the output signal tothe reset network.

[0017] An embodiment of a skewed NOR falling logic device of the presentinvention for rapidly propagating a falling edge of an output signalincludes a fast NOR gate falling having a large n/p channel width ratiofor receiving a first input signal and a second input signal and rapidlypropagating a falling edge of the output signal in response to a risingedge on either of the first input signal or the second input signal. Askewed NOR falling logic device may further include a pull-up resetnetwork connected in parallel with the fast NOR gate falling forresetting the output signal, and a feedback delay circuit connected inparallel with the pull-up reset network for propagating the outputsignal to an input of the pull-up reset network.

[0018] An embodiment of a skewed NOR rising logic device of the presentinvention for rapidly propagating a rising edge of an output signalincludes a fast NOR gate rising having a large p/n channel width ratiofor receiving a first input signal and a second input signal and rapidlypropagating a rising edge of the output signal in response to a fallingedge on both of the first input signal and the second input signal. Askewed NOR rising logic device may further include a pull-down resetnetwork connected in parallel with the fast NOR gate rising forresetting the output signal after the rising edge of the output signalhas been propagated, and a feedback delay circuit connected in parallelwith the pull-down reset network for delaying and returning the outputsignal back to an input of the pull-down reset network.

[0019] An embodiment of a skewed NAND falling logic device of thepresent invention for rapidly propagating a falling edge of an outputsignal includes a fast NAND gate falling having a large n/p channelwidth ratio for receiving both a first input signal and a second inputsignal and rapidly propagating a falling edge of the output signal inresponse to rising edges on both the first input signal and the secondinput signal. A skewed NAND falling logic device may further include apull-up reset network connected in parallel with the fast NAND gatefalling for resetting the output signal after the falling edge of theoutput signal has been propagated, and a feedback delay circuitconnected in parallel with the pull-up reset network for delaying andreturning the output signal to an input of the pull-up reset network.

[0020] An embodiment of a skewed NAND rising logic device of the presentinvention for rapidly propagating a rising edge of an output signalincludes a fast NAND gate rising having a large p/n channel width ratiofor receiving both a first input signal and a second input signal andrapidly propagating a rising edge of the output signal in response tofalling edges on either the first input signal or the second inputsignal. A skewed NAND rising logic device may further include apull-down reset network connected in parallel with the fast NAND gaterising for resetting the output signal after the rising edge of theoutput signal has been propagated, and a feedback delay circuitconnected in parallel with the pull-down reset network for delaying andreturning the output signal to an input of the pull-down reset network.

[0021] A method for rapidly propagating a fast edge of an output signalthrough a skewed logic device of the present invention is disclosed.Additionally, integrated circuits, substrates, computer systems, pulsestretchers and cascaded combinations of skewed logic devices of thepresent invention are also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In the drawings, which illustrate what is currently regarded asthe best mode for carrying out the invention and in which like referencenumerals refer to like parts in different views or embodiments:

[0023]FIG. 1 is a circuit diagram of a conventional static CMOSinverter.

[0024]FIG. 2 is a timing diagram for the conventional inverter of FIG. 1illustrating relative timing for input signal and output signals.

[0025]FIG. 3 is a schematic diagram of an embodiment of a skewedinverter rising logic device with a fast rising edge in accordance withthe present invention.

[0026]FIG. 4 is a timing diagram of the embodiment of a skewed inverterrising logic device shown in FIG. 3.

[0027]FIG. 5 is an expanded timing diagram corresponding to time t₀through time t₄ as indicated in FIG. 4 with input, output and internalnode signals superimposed.

[0028]FIG. 6 is an expanded timing diagram corresponding to time t₅through time t₇ as indicated in FIG. 4 with input, output and internalnode signals superimposed.

[0029]FIGS. 7A and 7B are logic diagrams of alternative combinationallogic suitable for use in a pull-down network of a skewed inverterrising logic device in accordance with the invention.

[0030]FIG. 8 is a schematic diagram of an embodiment of a skewedinverter falling logic device with a fast falling edge in accordancewith the invention.

[0031]FIG. 9 is a timing diagram of the embodiment of a skewed inverterfalling logic device with a fast falling edge shown in FIG. 8.

[0032]FIG. 10 is an expanded timing diagram corresponding to time t₈through time t₉ as indicated in FIG. 9 with input, output and internalnode signals superimposed.

[0033]FIG. 11 is an expanded timing diagram corresponding to time t₁₁through time t₁₅ as indicated in FIG. 9 with input, output and internalnode signals superimposed.

[0034]FIGS. 12A and 12B are schematic diagrams of alternativecombinational logic which may be used in the skewed inverter fallinglogic device of FIG. 8.

[0035]FIGS. 13A and 13B are schematic diagrams of downward and upwardpulse stretchers, respectively, incorporating skewed inverter logicdevices of the present invention.

[0036]FIG. 14 is schematic diagram of a skewed buffer rising logicdevice for rapidly propagating a rising edge of an output signal inaccordance with the present invention.

[0037]FIG. 15 is a schematic diagram of a skewed buffer falling logicdevice for rapidly propagating a rising a falling edge of an outputsignal in accordance with the present invention.

[0038]FIG. 16 is a schematic diagram of a skewed NOR falling logicdevice for rapidly propagating a falling edge of an output signal, inaccordance with the present invention.

[0039]FIG. 17 is a schematic diagram of a skewed NOR rising logic deviceconfigured for rapidly propagating a rising edge of an output signal inaccordance with the present invention.

[0040]FIG. 18 is a schematic diagram of a skewed NAND falling logicdevice configured for rapidly propagating a falling edge of an outputsignal in accordance with the prevent invention.

[0041]FIG. 19 is a schematic diagram of a skewed NAND rising logicdevice for rapidly propagating a rising edge of an output signal, inaccordance with the present invention.

[0042]FIG. 20 is block diagram of a memory device incorporating skewedlogic devices of the present invention.

[0043]FIG. 21 is a block diagram of a computer system incorporating atleast one of the skewed logic devices of the present invention.

[0044]FIG. 22 is a plan view of a semiconductor substrate incorporatingat least one of the skewed logic devices of the present invention.

[0045]FIG. 23 is a flow chart of a method for rapidly propagating anedge of an output signal through a skewed logic device in accordancewith the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0046] The invention includes digital logic devices with extremelyskewed trip points and reset circuitry for rapidly propagating signaledges, hereinafter “skewed logic devices.”Embodiments of skewed logicdevices in accordance with the present invention include inverters,buffers, NOR gates and NAND gates for rapidly propagating a selected“fast” edge of an input signal. Additional embodiments disclosed hereininclude pulse stretchers, memory devices, substrates, computer systemsand methods incorporating the skewed logic devices of the presentinvention.

[0047] The term “high” is used herein to indicate the state of anelectrical signal at a logical true or high voltage condition, forexample, supply voltage or 2.5 volts. The invention is not dependent onthe particular supply voltage which may, for example and not by way oflimitation, range from about 5.0 volts to about 1.5 volts depending onthe device technology used. The term “low” is used herein to indicatethe state of an electrical signal at a logical false or low voltagecondition, for example, ground potential or zero (0) volts.Additionally, the invention is not dependent on the magnitude of thefull voltage swing from ground potential to supply voltage, i.e.,rail-to-rail voltage. The terms “signal” and “node” may be usedsynonymously herein to indicate an electrically conductive circuit tracethat may connect an electrical device input or output to one or moreother device inputs or outputs, or supply or ground potential voltages.

[0048]FIG. 3 is a schematic diagram of a skewed inverter rising logicdevice 300 for rapidly propagating a rising edge of an output signal OUTin accordance with the present invention. Skewed inverter rising logicdevice 300 includes fast inverter 302, pull-down reset network 330 andfeedback delay circuit 340. External signals of the skewed inverterrising logic device 300 include input signal IN and output signal OUT.Input signal IN is input to fast inverter 302. Fast inverter 302directly drives output signal OUT.

[0049] As known to one of ordinary skill in the art, channel width isdirectly proportional to the gain of a MOS transistor. One of ordinaryskill in the art will also recognize that a plurality of MOS transistorsmay be placed in parallel with gates, drains and sources coupledtogether to effectively increase the gain of a single MOS transistor.Thus, the exemplary transistors illustrated herein may be modified insuch ways known to one of ordinary skill in the art and still be withinthe scope of the present invention. Fast inverter 302 is configured witha relatively wide p-channel (denoted “BIG P”) and a relatively narrown-channel (denoted “SMALL N”) and thus, will rapidly propagate therising edge of an output signal OUT. Because the p-channel issignificantly wider than the n-channel, the rising edge of an outputsignal OUT will propagate more rapidly than a rising edge propagatingthrough a conventional CMOS inverter with similarly sized p-channel andn-channel widths. An embodiment of fast inverter 302 may include a PMOStransistor (not shown) with a relatively wide p-channel and acomplementary NMOS transistor (also not shown) with a relatively narrown-channel.

[0050] By “skewing” the width of a particular channel relative to theother channel, the trip-point of a transistor may also be “skewed,”resulting in a selected “fast” edge of an output signal OUT propagatingmore rapidly than the other “slow” edge. Thus, the relative widths ofthe n-channel and p-channel which form the skewed logic devices of thepresent invention may be significantly uneven, relative to conventionalCMOS logic devices. The terms “relatively wide” or “large” as associatedwith a channel width ratio herein are used synonymously and may bemeasured by a p/n channel width ratio or conversely an n/p channel widthratio of the devices (MOS transistors) that are used to form the “fast”gates of the skewed logic devices.

[0051] Similarly, the terms “BIG,” “wide” and “relatively wide” inreference to channel widths of a given transistor (NMOS or PMOS) areused synonymously herein and are relative to a conventional channelwidth for the same transistor for a given manufacturing process. Theratio of the “BIG” transistor channel width over the conventionalchannel width forms a “channel width ratio” useful for describing a“BIG” transistor. For example, and not by way of limitation, if a PMOStransistor may be conventionally formed with a 10 μm p-channel inaccordance with a given manufacturing process and a “BIG” PMOStransistor has a p-channel of 2000 μm in width, the “channel widthratio” will be 200. Thus, a “BIG” transistor has a channel width ratiogreater than 1.0 relative to a conventional channel width for the sametransistor. Another measure which may be useful for describing a “BIG”transistor is a channel width greater than 10 μm. However, asmanufacturing processes continually reduce the scale of featuredimensions, the standard channel width for NMOS and PMOS transistorswill likely reduce in size as well. So, the term “BIG” associated withchannel width and as used herein is preferably measured relative to aconventional or smallest channel width for a given manufacturingprocess.

[0052] The rapid edge propagation of the skewed logic devices of thepresent invention is a gradual effect beginning with a p/n channel widthratio, or conversely an n/p channel width ratio, of greater than 1.0 andhaving an upper range only limited by space for the physical layout ofthe device. Preferably, the p/n, or n/p, channel width ratio should bein the range from about 5 to about 200. Thus, a “relatively Wide” n/pchannel width ratio, or p/n channel width ratio, is preferably in therange from about 5 to about 200. Larger ratios are also possible but maybe less preferable depending on the particular physical layout and spacelimitations of the semiconductor device manufacturing process used toform the skewed logic devices of the present invention.

[0053] A significant purpose of feedback delay circuit 340 is toindicate the state of the output signal OUT to pull-down reset network330. The length of the delay of feedback delay circuit 340 must begreater than the sum of the slew rate of the output signal OUT and theRC delay of the line being driven by pull-down reset network 330. Asshown in FIG. 3, feedback delay circuit 340 may include four inverters315, 316, 318 and 320. Feedback delay circuit 340 delays and returnsoutput signal OUT through a series of inverters 315, 316, 318 and 320and ultimately outputs signal NET120 to an input of pull-down resetnetwork 330. More specifically, output signal OUT is input to inverter315. The output of inverter 315 is input to inverter 316. The output ofinverter 316 is input to inverter 318. The output of inverter 318 isinput to inverter 320. The output of inverter 320 is NET120. Of course,many other logically equivalent structures with a suitable delay thatensures the output is fully reset may be substituted for the fourinverters 315, 316, 318, 320, as shown in the feedback delay circuit 340of FIG. 3. For example, and not by way of limitation, four buffersconnected in series, or four delay elements connected in series, may besubstituted for the four inverters 315, 316, 318, 320. Such otherlogically equivalent structures will be within the knowledge of one ofordinary skill in the art and are also contemplated as being within thescope of the present invention.

[0054] Pull-down reset network 330 includes combinational logic 350 andbig NMOS transistor 308. Combinational logic 350 may include NAND gate304 and inverter 306, as shown in FIG. 3. Alternatively, combinationallogic 350 may include other suitable combinations of logic gates, seeFIGS. 7A and 7B and related discussion below. Pull-down reset network330 has two inputs and one output. The inputs of pull-down reset network330 correspond to first and second inputs of NAND gate 304. The firstinput of NAND gate 304 is input signal IN and the second input signal ofNAND gate 304 is NET120. The output of NAND gate 304 is input toinverter 306. The signal NET122 of inverter 306 drives a gate node ofbig NMOS transistor 308. A drain node of big NMOS transistor 308 isconnected to output signal OUT and a source node is coupled to groundpotential GND. Big NMOS transistor 308 has a relatively wide n-channel(denoted “BIG N” in FIG. 3) and thus, is configured for rapidlyswitching the output signal OUT in response to a high voltage. Arelatively wide channel, or “BIG” channel width, whether n-type orp-type, may be in the range of approximately 10 μm to approximately 10mm in width.

[0055] The operation of the skewed inverter rising logic device 300shown in FIG. 3 is described with reference to the timing diagram ofFIG. 4. FIG. 4 is a timing diagram of signals IN, OUT, NET120 and NET122as shown in the skewed inverter rising logic device 300 of FIG. 3. Justprior to time t₀, input signal IN is low, output signal OUT is high,node NET120 is high and node NET122 is low. Beginning at time t₀, inputsignal IN transitions high, driving the output signal OUT low. The smallNMOS transistor (n-channel) of fast inverter 302 attempts to pull outputsignal OUT low; however, pull-down reset network 330 actually drives theoutput signal OUT low with little help from the small n-channel of theNMOS transistor of fast inverter 302, as explained in further detailbelow.

[0056] The transition of input signal IN from low to high is propagatedthrough pull-down reset network 330 during time period t₁. Morespecifically, as input signal IN transitions high, both inputs, IN andNET120, to NAND gate 304 are high, which changes the output of NAND gate304 to low. The low output from NAND gate 304 is input to inverter 306,which, in turn, changes signal NET122 to a high, driving the gate of bigNMOS transistor 308. Because big NMOS transistor 308 has a “big”n-channel, the output signal OUT is then rapidly pulled low during timeperiod t₂. The small n-channel of fast inverter 302 reinforces the lowvoltage on output signal OUT.

[0057] The transition of output signal OUT from high to low propagatesthrough feedback delay circuit 340 during time period t3. When outputsignal OUT goes low, inverter 315 outputs a high. The high output ofinverter 315 is input to inverter 316, driving the output of inverter316 low, which in turn drives the output of inverter 318 high, and thendrives the output NET120 of inverter 320 low as shown in FIG. 4.

[0058] The transition of NET120 low propagates through pull-down resetnetwork 330 during time period t₄, turning big NMOS transistor 308 off.More specifically, with NET120 low and input signal IN high, the outputof NAND gate 304 goes high. The high input to inverter 306 drives NET122low, which turns big NMOS transistor 308 off, leaving output signal OUTlow. Again, the small NMOS transistor of fast inverter 302 actively, butweakly, holds the output signal OUT low.

[0059] At time t₅, input signal IN is high, output signal OUT is low,NET120 is low and NET 122 is low. As input signal IN transitions lowduring time period t₆, output signal OUT rapidly transitions highthrough fast inverter 302. The transition of the output signal OUT tohigh drives node NET120 high during time period t7. More specifically, ahigh on output signal OUT drives the output of inverter 315 low. The lowinput to inverter 316 drives the output of inverter 316 to high, whichin turn drives the output of inverter 318 low, which in turn drives theoutput of inverter 320, or node NET120, high as shown in FIG. 4. Afternode NET120 transitions high during time period t₇, the skewed inverterrising logic device 300 is back to its initial state, as it was justprior to t₀.

[0060]FIG. 5 is an expanded timing diagram corresponding to time t₀through time period t4 as indicated in FIG. 4 with signals IN, OUT,NET120 and NET122 superimposed. FIG. 5 also illustrates the period oftime for input signal IN to go high and output signal OUT to go low,t_(hl).

[0061]FIG. 6 is an expanded timing diagram corresponding to time t5through time period t₇ as indicated in FIG. 4 with signals IN, OUT,NET120 and NET122 superimposed. FIG. 6 also illustrates the period oftime for input signal IN to go low and output signal OUT to go high,t_(lh). The short duration of time period t_(lh), during which outputsignal OUT transitions from low to high, is extremely fast andcomparable to the speeds obtained with conventional domino logic.

[0062] As noted above, one of ordinary skill in the art will recognizethat there are other combinations of logic gates that are equivalent infunction and timing to combinational logic 350, i.e., that perform anAND function with approximately two gate delays and thus, may besubstituted for same. For example, FIGS. 7A and 7B are logic diagrams ofalternative combinational logic 350A and 350B that perform a logical ANDfunction using two gates to reduce input and output loading and aresuitable for use in a pull-down network of a skewed inverter risinglogic device in accordance with the present invention.

[0063]FIG. 7A is a logic diagram of alternative combinational logic 350Awhich may be used in place of combinational logic 350. Combinationallogic 350A includes inverter 750, inverter 752 and NOR gate 754. Morespecifically, input signal IN is input to inverter 750, and NET120 isinput to inverter 752. The outputs of inverters 750 and 752 are input toNOR gate 754. The output of NOR gate 754 drives NET122. FIG. 7B is alogic diagram of another alternative combinational logic 350B that maybe substituted for combinational logic 350. Combinational logic 350Bincludes AND gate 760 and delay element 762. More specifically, inputsignal IN and NET 120 are input to AND gate 760. The output of AND gate760 is input to delay element 762. The output of delay element 762drives NET 122. Combinational logic 350, 350A and 350B are merelyexemplary and not to be construed as the only logically equivalentcombinations of gates that may be used in a skewed inverter rising logicdevice 300 according to the present invention. Other logicallyequivalent combinations of gates producing an “AND” function with twogate delays may also be used with the skewed inverter rising logicdevice 300, and are thus also within the scope of the invention.

[0064]FIG. 8 is a schematic diagram of an embodiment of a skewedinverter falling logic device 800 in accordance with the presentinvention. Skewed inverter falling logic device 800 includes fastinverter 802, pull-up reset network 830 and feedback delay circuit 840.The external signals of the skewed inverter falling logic device 800 areinput signal IN and output signal OUT. Input signal IN is input to fastinverter 802. Fast inverter 802 directly drives output signal OUT. Fastinverter 802 has an NMOS transistor (not shown) having a relatively widen-channel width (denoted “BIG N” in FIG. 8) and a complementary PMOStransistor (not shown) having a relatively narrow p-channel width(denoted “SMALL P” in FIG. 8). Because of the large n/p channel widthratio, a falling edge of an output signal OUT will propagate veryrapidly through fast inverter 802.

[0065] Pull-up reset network 830 may include combinational logic 850 andbig PMOS transistor 808. Note that big PMOS transistor 808 has arelatively wide p-channel (denoted “BIG P” in FIG. 8), thus facilitatinghigh-speed switching when big PMOS transistor 808 turns on, i.e., whenreceiving a low on signal NET21 or the gate node of big PMOS transistor808. As shown in FIG. 8, combinational logic 850 includes the seriescombination of NOR gate 804 and inverter 806. Of course, one of skill inthe art will recognize that other combinations of logic gates may beused to accomplish a logical “OR” function and timing of combinationallogic 850, for example and not by way of limitation, see FIGS. 12A and12B and related discussion below.

[0066] Pull-up reset network 830 includes two inputs and selectivelydrives big PMOS transistor 808. More specifically, input signal IN andnode NET23 are inputs to NOR gate 804. The output of NOR gate 804 isinput to inverter 806, which in turn outputs node NET21. Node NET21drives the gate node of big PMOS transistor 808. The source node of bigPMOS transistor 808 is coupled to the supply voltage, VDD. The drainnode of big PMOS transistor 808 is coupled to output signal OUT. Thus,when node NET21 is low, big PMOS transistor 808 pulls the output signalOUT to supply voltage, VDD.

[0067] Feedback delay circuit 840 may include four serially connectedinverters 812, 814, 816 and 818. Output signal OUT is input to feedbackdelay circuit 840 which outputs signal NET23. More specifically, outputsignal OUT is input to inverter 812. The output of inverter 812 is inputto inverter 814. The output of inverter 814 is input to inverter 816.The output of inverter 818 is node NET23. One of ordinary skill in theart will recognize that each inverter 812, 814, 816 and 818 may beimplemented with two or more MOS transistors appropriately configured.Other suitable combinations of logic gates having equivalent logicalfunction and timing may be substituted for inverters 812, 814, 816 and818. For example and not by way of limitation, four serially connectedbuffers or two serially connected buffers and two serially connectedinverters may be substituted for inverters 812, 814, 816 and 818,consistent with the present invention. Such substitutions arecontemplated as being within the scope of the present invention.

[0068] The operation of skewed inverter falling logic device 800, asshown in FIG. 8, is described with reference to the timing diagram ofFIG. 9. FIG. 9 is a timing diagram of signals IN, OUT, NET21 and NET23as shown in FIG. 8. At time t₈, input signal IN is low, output signalOUT is high, node NET21 is high and node NET23 is high. During time t₉,input signal IN transitions high, rapidly driving the output signal OUTlow.

[0069] The transition of input signal IN from low to high during timeperiod t₉ does not propagate through pull-up reset network 830. Morespecifically, at time t₈, the inputs to NOR gate 804 are low and highfrom input signals IN and NET23, respectively. Thus, the output of NORgate 804 at time t₈ is low. When input signal IN transitions high, bothinputs to NOR gate 804 are high and the output is still low.

[0070] However, the transition of output signal OUT from high to lowduring time period t₁₀ propagates through feedback delay circuit 840,causing node NET23 to transition low. More specifically, with outputsignal OUT low, the output of inverter 812 goes high. The high input toinverter 814 results in an output low, which in turn causes inverter 816to output high and, finally, inverter 818 to drive node NET23 low.

[0071] At time t₁₁, input signal IN is high, output signal OUT is low,NET21 is high and NET23 is low. The transition of input signal IN fromhigh to low during time period t₁₂ propagates through NOR gate 804 andinverter 806. More specifically, a low on both input signal IN and NET23causes NOR gate 804 to output high. The high input to inverter 806drives NET21 low. A low on NET21 turns on big PMOS transistor 808, thusresetting the output signal OUT to a high during time period t₁₂. Asinput signal IN transitions low beginning at time t₁₁, output signal OUTbegins to transition to a high state through fast inverter 802. Fastinverter 802 is unable to switch the output signal OUT by itself.However, with a “SMALL P” channel, fast inverter 802 reinforces the highestablished by the big PMOS transistor 808.

[0072] The rising edge of output signal OUT propagates through feedbackdelay circuit 840, causing node NET23 to transition high during timeperiod t₁₄. More specifically, with output signal OUT high, inverter 812outputs low. A low input to inverter 814 drives the input to inverter816 high, causing inverter 816 to output low. The low input to inverter818 drives node NET23 high. The rising edge of node NET23 propagatesthrough pull-up reset network 830 and turns off big PMOS transistor 808during time period t₁₅. More specifically, as NET23 transitions high,with input signal IN low, the output of NOR gate 804 goes low. The lowinput to inverter 806 drives NET21 high, turning off big PMOS transistor808.

[0073]FIG. 10 is an expanded timing diagram corresponding to time t8through time period t₉ as indicated in FIG. 9 with signals IN, OUT,NET21 and NET23 superimposed. FIG. 10 also illustrates the period oftime, t_(hl), for input signal IN to go high and output signal OUT to golow. The short duration of time period t_(hl), during which outputsignal OUT transitions from high to low, is extremely fast relative toconventional (unskewed CMOS circuitry) and comparable to the speedsobtained with conventional domino logic.

[0074]FIG. 11 is an expanded timing diagram corresponding to time t₁₁through time period t₁₅ as indicated in FIG. 9 with signals IN, OUT,NET21 and NET23 superimposed. FIG. 11 also illustrates the period oftime, t_(lh), for input signal IN to go low and output signal OUT to gohigh.

[0075]FIGS. 12A and 12B are logic diagrams of alternative combinationallogic (850A and 850B, respectively) which may be used in the skewedinverter falling logic device 800 of FIG. 8. Referring to FIG. 12A,combinational logic 850A includes inverter 1202, inverter 1204 and NANDgate 1206. More specifically, input signal IN is input to inverter 1204,and node NET23 is input to inverter 1202. The outputs of inverters 1202and 1204 are input to NAND gate 1206. The output of NAND gate 1206drives node NET21. One of ordinary skill in the art will recognize thatinverters 1202 and 1204 in combination with NAND gate 1206 as shown inFIG. 12 are logically and timing equivalent to NOR gate 804 and inverter806 as configured and shown in FIG. 8. Referring to FIG. 12B,combinational logic 850B includes OR gate 1208 and delay element 1210.More specifically, input signal IN and NET23 are input to OR gate 1208.The output of OR gate 1208 is input to delay element 1210. The output ofdelay element 1210 drives NET21. Combinational logic 850, 850A and 850Bare merely exemplary embodiments of combinational logic suitable for usewith skewed inverter falling logic device 800. Other logicallyequivalent combinations of gates producing an “OR” function with twogate delays may be substituted for combinational logic 850, 850A and850B and are contemplated within the scope of the invention.

[0076] The skewed inverters 300, 800 of the present invention may beused in logic circuits to perform many different functions in additionto inverting an input signal. The term “skewed inverter,” by itself, isinclusive of the terms “skewed inverter rising logic device” and “skewedinverter falling logic device.” The term “skewed inverter rising logicdevice” 300 may also be referred to herein by the acronym “SKINVR” 300or simply “skewed inverter rising” 300. Similarly, the term “skewedinverter falling logic device” 800 may also be referred to herein by theacronym “SKINVF” 800 or simply “skewed inverter falling” 800. A seriesof alternating SKINVR 300 and SKINVF 800 may be used to rapidlypropagate rising and falling edges.

[0077] Referring to FIG. 13A, a SKINVR 300 may be used serially with aSKINVF 800 as a downward pulse stretcher 1300A for an input downwardpulse. The operation of a downward pulse stretcher 1300A is as follows.A downward pulse 1302 is input to a SKINVR 300. The output of SKINVR 300is input to SKINVF 800. The output of SKINVF 800 is a wider or“stretched” downward pulse 1304. FIG. 13B illustrates a schematicdiagram of an upward pulse stretcher 1300B. Upward pulse stretcher 1300Bincludes serially connected SKINVF 800 with SKINVR 300. The operation ofan upward pulse stretcher 1300B includes inputting an upward pulse 1306into SKINVF 800. The output of SKINVF 800 is input to SKINVR 300. Theoutput of SKINVR 300 is a wider or “stretched” upward pulse 1308. Oneskilled in the art will recognize that any number of downward pulsestretchers 1300A or upward pulse stretchers 1300B may be connected inseries to effect further pulse stretching. Additionally, one skilled inthe art will recognize that pulse stretchers that invert, i.e., an inputupward pulse, output as a stretched downward pulse, or vice versa, mayalso be formed of serial combinations of SKINVR 300 and SKINVF 800devices. Other skewed logic devices may be formed using logic gates withskewed trip points similar to those illustrated above.

[0078]FIG. 14 is a schematic diagram of a skewed buffer rising logicdevice 1400 for rapidly propagating a rising edge of an output signalOUT, in accordance with the present invention. Skewed buffer risinglogic device 1400 includes a fast inverter falling 1402, a fast inverterrising 1404, a reset network 1430 and a feedback delay circuit 1440.Fast inverter falling 1402 includes a large n/p channel width ratio(denoted “SMALL P” and “BIG N” in FIG. 14) for receiving a rising edgeof an input signal IN and rapidly propagating a falling edge of anintermediate signal A in response thereto. The input to fast inverterfalling 1402 is input signal IN. Intermediate signal A is input to fastinverter rising 1404. The output of fast inverter rising 1404 is outputsignal OUT. Fast inverter rising 1404 includes a large p/n channel widthratio (denoted “BIG P” and “SMALL N” in FIG. 14) and receives therapidly propagated falling edge of intermediate signal A and rapidlypropagates a rising edge on the output signal OUT. Reset network 1430 isconnected to fast inverter falling 1402 and fast inverter rising 1404and resets output signals of fast inverter falling 1402 and fastinverter rising 1404 after the rising edge of an output signal OUT hasbeen rapidly propagated. Feedback delay circuit 1440 is connectedbetween an output of fast inverter rising 1404 and an input of resetnetwork 1430 for propagating output signal OUT to the reset network1430.

[0079] Reset network 1430 includes combinational logic 1410 forreceiving input signal IN and a PMOS pull-up transistor 1412 having awide p-channel (denoted “BIG P”) with a gate node driven by an output ofthe combinational logic 1410, a source node connected to supply voltageVDD and a drain node connected to intermediate signal A for pullingintermediate signal A up to supply voltage VDD in response to a lowsignal on the gate node. Reset network 1430 also includes an inverter1414 having an input connected to the gate node of PMOS pull-uptransistor 1412 and an NMOS pull-down transistor 1416 having a widen-channel (denoted “BIG N”) having a gate node connected to the outputof inverter 1414, a drain node connected to output signal OUT and asource node connected to ground potential GND.

[0080] Combinational logic 1410 performs a logical “OR” function.Combinational logic 1410, as shown in FIG. 14, may include a NOR gate1418 with a first input connected to input signal IN and a second inputconnected to an output of feedback delay circuit 1440. Combinationallogic 1410 may further include inverter 1420 having input connected tothe output of NOR gate 1418 and having an output connected to the gatenode of PMOS pull-up transistor 1412. Of course, other logicallyequivalent and timing equivalent combinations of logic gates may besubstituted for NOR gate 1418 and inverter 1420 of combinational logic1410 and still remain within the scope of the present invention.

[0081] Feedback delay circuit 1440 may include five serially connectedinverters 1422, 1424, 1426, 1428 and 1408 as shown in FIG. 14. Ofcourse, other logically equivalent combinations of logic gates havingabout five gate delays may also be substituted for the five seriallyconnected inverters 1422, 1424, 1426, 1428 and 1408, as known to one ofordinary skill in the art, and yet remain within the scope of thepresent invention.

[0082]FIG. 15 is a schematic of a skewed buffer falling logic device1500 for rapidly propagating a falling edge of an output signal OUT, inaccordance with the present invention. Skewed buffer falling logicdevice 1500 includes a fast inverter rising 1502, fast inverter falling1504, a reset network 1530 and a feedback delay network 1440. Inputsignal IN is input to fast inverter rising 1502, which in turn outputsintermediate signal B. Fast inverter rising 1502 includes a large p/nchannel width ratio (denoted “BIG P” and “SMALL N” in FIG. 15) forreceiving a falling edge of input signal IN and rapidly propagating arising edge of intermediate signal B in response thereto. Fast inverterfalling 1504 is connected in series with fast inverter rising 1502 forreceiving intermediate signal B and rapidly propagated a falling edge onthe output signal OUT. Fast inverter falling 1504 includes a large n/pchannel width ratio, denoted “SMALL P” and “BIG N” in FIG. 15.

[0083] Reset network 1530 is connected to fast inverter rising 1502 andto fast inverter falling 1504 and resets output signals of both fastinverter rising 1502 and fast inverter falling 1504 after the fallingedge of output signal OUT has been rapidly propagated through skewedbuffer falling logic device 1500. Reset network 1530 may includecombinational logic 1510 for receiving input signal IN and an NMOSpull-down transistor 1512 having a wide n-channel (denoted “BIG N”), agate node connected to the output of combinational logic 1510, a drainnode connected to intermediate signal B and a source node connected toground potential, GND. Reset network 1530 may further include aninverter 1514 having input connected to the gate node of NMOS pull-downtransistor 1512 and a PMOS pull-up transistor 1516 having a widep-channel (denoted “BIG P”) and having a gate node driven by inverter1514, a source node connected to supply voltage VDD and a drain nodeconnected to output signal OUT. Feedback delay circuit 1440 is connectedbetween the output of fast inverter falling 1504 and an input of resetnetwork 1530 for propagating output signal OUT to reset network 1530.

[0084] Combinational logic 1510 performs a logical “AND” function withabout two gate delays. Combinational logic 1510 may include a NAND gate1518 with a first input connected to the input signal IN and a secondinput connected to an output of feedback delay circuit 1440.Combinational logic 1510 may further include inverter 1520 having aninput connected to the output of NAND gate 1518 and having an outputconnected to the gate node of the NMOS pull-down transistor 1512. Ofcourse, other logically equivalent and timing equivalent combinations oflogic gates may be substituted for combinational logic 1510 and stillremain within the scope of the present invention.

[0085]FIG. 16 is a schematic diagram of a skewed NOR falling logicdevice 1600 for rapidly propagating a falling edge of an output signalOUT, in accordance with the present invention. Skewed NOR falling logicdevice 1600 may include a fast NOR gate falling 1602, a pull-up resetnetwork 1630 and a feedback delay circuit 1640, as shown in FIG. 16.Fast NOR gate falling 1602 includes a large n/p channel width ratio(denoted “BIG N” and “SMALL P” in FIG. 16) for receiving first andsecond input signals and rapidly propagating a falling edge of theoutput signal OUT in response to a rising edge on either of the firstinput signal INA or the second input signal INB.

[0086] Pull-up reset network 1630 is connected in parallel with fast NORgate falling 1602 for resetting output signal OUT after the “fast” edge,i.e., a falling edge, has been propagated to output signal OUT. Pull-upreset network 1630 may include combinational logic 1650 and a big PMOStransistor 1608. Combinational logic 1650, as shown in FIG. 16, mayinclude a 3-input NOR gate 1604 in series with inverter 1606, which inturn drives the gate node of big PMOS transistor 1608. Three-input NORgate 1604 has a first input connected to first input signal INA, asecond input connected to second input signal INB, a third inputconnected to the output of feedback delay circuit 1640 and an outputconnected to the input of inverter 1606. Big PMOS transistor 1608 has awide p-channel (denoted “BIG P”) with a gate node connected to theoutput of combinational logic 1650, a source node connected to supplyvoltage VDD and a drain node connected to the output signal OUT.Combinational logic 1650 performs a logical “OR” function withapproximately two gate delays. Of course, other logically equivalent andtiming equivalent combinations of logic gates may be substituted for thecombinational logic 1650 by one of ordinary skill in the art, withoutdeparting from the scope of the present invention.

[0087] Feedback delay circuit 1640 propagates the output signal OUTthrough feedback delay circuit 1640 and provides the delayed outputsignal OUT as an input to pull-up reset network 1630. Thus, feedbackdelay circuit 1640 is connected in parallel with pull-up reset network1630. As shown in FIG. 16, feedback delay circuit 1640 may include fourinverters 1610, 1612, 1614 and 1616 connected in series and providing adelay of approximately four gate delays in duration. Of course, othersuitable combinations of logic gates and/or delay elements may besubstituted for the four inverters 1610, 1612, 1614 and 1616 of feedbackdelay circuit 1640. Such substitutions are within the knowledge of oneof ordinary skill in the art and are within the scope of the presentinvention.

[0088]FIG. 17 is a schematic diagram of a skewed NOR rising logic device1700 for rapidly propagating a rising edge of an output signal OUT, inaccordance with the present invention. Skewed NOR rising logic device1700 includes fast NOR gate rising 1702, pull-down reset network 1730and feedback delay circuit 1640. Note that fast NOR gate rising 1702 isdenoted “BIG P” and “SMALL N” for relatively wide p-channel widths andrelatively narrow n-channel widths and thus, will rapidly propagate therising edge of output signal OUT in response to a falling edge on boththe first input signal INA and the second input signal INB. Pull-downreset network 1730 is connected in parallel with fast NOR gate rising1702. Feedback delay circuit 1640 is connected in parallel withpull-down reset network 1730, and may include four inverters 1610, 1612,1614 and 1616 connected in series, providing a delay of approximatelyfour gate delays in duration.

[0089] Pull-down reset network 1730 may include combinational logic 1750connected to pull-down NMOS transistor 1708. Pull-down NMOS transistor1708 includes a relatively wide n-channel (denoted “BIG N”).Combinational logic 1750 receives inputs from input signals INA and INBand also receives an input from the output of feedback delay circuit1640. Combinational logic 1750 performs a logical “sum of products”function with a delay of approximately two gate delays in duration. Asshown in FIG. 17, combinational logic 1750 may include three NAND gates1704, 1706 and 1710. NAND gate 1704 has a first input connected to firstinput signal INA, a second input connected to the output of feedbackdelay circuit 1640 and an output connected to a first input of NAND gate1710. NAND gate 1706 has a first input connected to second input signalINB, a second input connected to the output of feedback delay circuit1640 and an output connected to a second input of NAND gate 1710. Theoutput of NAND gate 1710 is connected to a gate node of pull-down NMOStransistor 1708. Of course, other suitable combinations of logic gatesperforming a logical “sum of products” function with a delay ofapproximately two gate delays in duration may be substituted for thecombinational logic 1750. Such logical equivalents are within theknowledge of one of ordinary skill in the art and are also contemplatedas being within the scope of the present invention.

[0090]FIG. 18 is a logic diagram of a skewed NAND falling logic device1800 for rapidly propagating a falling edge of an output signal OUT, inaccordance with the present invention. Skewed NAND falling logic device1800 includes fast NAND gate falling 1802, pull-up reset network 1830and feedback delay circuit 1640. Note that fast NAND gate falling 1802has a relatively large n/p channel width ratio (denoted “SMALL P” and“BIG N”) for relatively wide n-channel widths and relatively narrowp-channel widths and thus, will rapidly propagate the falling edge of anoutput signal OUT in response to rising edges on both the first inputsignal INA and the second input signal INB. Pull-up reset network 1830is connected in parallel with fast NAND gate falling 1802. Feedbackdelay circuit 1640 is connected in parallel with pull-up reset network1830. Feedback delay circuit 1640 may include four inverters 1610, 1612,1614 and 1616 connected in series, providing a delay of approximatelyfour gate delays in duration.

[0091] Pull-up reset network 1830, as shown in FIG. 18, may includecombinational logic 1850 connected to big PMOS transistor 1808. Notealso that big PMOS transistor 1808 has a relatively wide p-channel(denoted “BIG P”). Combinational logic 1850 receives inputs from inputsignals INA and INB and also receives input from the output of feedbackdelay circuit 1640. Combinational logic 1850 performs a logical “productof sums” function having a delay of approximately two gate delays induration. Combinational logic 1850 may include three NOR gates 1804,1806 and 1810, as shown in FIG. 18. NOR gate 1804 has a first inputconnected to first input signal INA, a second input connected to theoutput of feedback delay circuit 1640 and an output connected to a firstinput of NOR gate 1810. NOR gate 1806 has a first input connected tosecond input signal INB, a second input connected to the output offeedback delay circuit 1640 and an output connected to a second input ofNOR gate 1810. The output of NOR gate 1810 is connected to a gate nodeof big PMOS transistor 1808. Of course, other suitable combinations oflogic gates that perform a logical “product of sums” function with adelay of approximately two gate delays may be substituted forcombinational logic 1850. Such logical equivalents are within theknowledge of one of ordinary skill in the art and are also contemplatedas being within the scope of the present invention.

[0092]FIG. 19 is a schematic diagram of a skewed NAND rising logicdevice 1900 for rapidly propagating a rising edge of an output signalOUT, in accordance with the present invention. As shown in FIG. 19, askewed NAND rising logic device 1900 may include a fast NAND gate rising1902, a pull-down reset network 1930 and a feedback delay circuit 1640.Fast NAND gate rising 1902 includes a large p/n channel width ratio(denoted “BIG P” and “SMALL N”) for receiving a first input signal INAand a second input signal INB and rapidly propagating a rising edge ofthe output signal OUT in response to falling edges on either the firstinput signal INA or the second input signal INB. Feedback delay circuit1640 is connected in parallel with the pull-down reset network 1930 fordelaying and returning the output signal OUT to an input of thepull-down reset network 1930. Feedback delay circuit 1640 may includefour inverters 1610, 1612, 1614 and 1616 connected in series, providinga delay of approximately four gate delays in duration.

[0093] Pull-down reset network 1930 is connected in parallel with fastNAND gate rising 1902 for resetting the output signal OUT after therising edge of the output signal OUT has been propagated. Pull-downreset network 1930 may include combinational logic 1950 having threeinputs and an output, and a big NMOS transistor 1908 having a widen-channel (denoted “BIG N”), and having a gate node connected to theoutput of combinational logic 1950, a drain node connected to outputsignal OUT and a source node connected to ground potential GND.Combinational logic 1950 performs a logical AND function with a delay ofapproximately two gate delays in duration. As shown in FIG. 19,combinational logic 1950 may include a 3-input NAND gate 1904 having afirst input connected to the first input signal INA and a second inputconnected to the second input signal INB and a third input connected tothe output of feedback delay circuit 1640. Combinational logic 1950 mayfurther include an inverter 1906 having an input connected to the outputof 3-input NAND gate 1904 and having an output connected to, anddriving, the gate node of big NMOS transistor 1908. Of course, othersuitable combinations of logic gates that perform a logical AND functionwith a delay of approximately two gate delays may be substituted forcombinational logic 1950, as shown in FIG. 19. Such logical equivalentsare within the knowledge of one of ordinary skill in the art and arealso contemplated as being within the scope of the present invention.

[0094] The skewed logic devices 300, 800, 1400, 1500, 1600, 1700, 1800and 1900 of the present invention (hereinafter “skewed logic devices”)may be used in any higher order logical device where fast edgepropagation is desired. For example, and not by way of limitation, oneor more skewed logic devices may be used for fast selection in a decodefor a column select in a memory device. FIG. 20 illustrates a memorydevice 2000. Memory device 2000 includes decode logic 2002 incorporatingone or more skewed logic devices of the present invention. Memory device2000 may be, for example and not by way of limitation, a dynamic randomaccess memory (DRAM), double data rate SDRAM (DDR SDRAM), RAMBUS® DRAM(RDRAM®), extended data-out DRAM (EDO DRAM), fast-page-mode DRAM (FPMDRAM), static random access memory (SRAM), SyncBurst™ SRAM, Zero BusTurnaround™ SRAM (ZBT™ SRAM), Quad Data Rate™ SRAM (QDR™ SRAM), DDRsynchronous SRAM (DDR SRAM) and nonvolatile electrically block-erasableprogrammable read only memory (Flash).

[0095] Referring to FIG. 21, a block diagram of a computer system 2100incorporating skewed logic devices in accordance with the presentinvention is shown. Computer system 2100 includes an input device 2102,an output device 2104, a processor device 2106 connected to the inputdevice 2102 and the output device 2104 and a memory device 2108connected to the processor device 2106. The memory device 2108 includesskewed logic devices 300, 800, 1400, 1500, 1600, 1700, 1800, 1900 of thepresent invention. Memory device 2108 may be, for example and not by wayof limitation, a dynamic random access memory (DRAM), double data rateSDRAM (DDR SDRAM), RAMBUS® DRAM (RDRAM®), extended data-out DRAM (EDODRAM), fast-page-mode DRAM (FPM DRAM), static random access memory(SRAM), SyncBurst™ SRAM, Zero Bus Turnaround™ SRAM (ZBT™ SRAM), QuadData Rate™ SRAM (QDR™ SRAM), DDR synchronous SRAM (DDR SRAM) andnonvolatile electrically block-erasable programmable read only memory(Flash), as shown in FIG. 20.

[0096] Referring to FIG. 22, a plan view of a semiconductor substrate2200 including at least one integrated circuit die 2202 (only one ofwhich is shown for clarity). Each integrated circuit die 2202 includesat least one skewed logic device 300, 800, 1400, 1500, 1600, 1700, 1800,1900 in accordance with the invention. Integrated circuit die 2202 maybe a memory device 2000 as shown in FIG. 20, or it may be any otherintegrated circuit die that includes a skewed logic device of thepresent invention.

[0097] The semiconductor technology employed is not a limiting factor inthe application of the skewed logic devices of the present invention.While silicon is the preferred bulk semiconductor material forcommercial electronic devices, gallium arsenide and indium phosphidesubstrates may also be employed. Of course, it will be understood thatthe skewed logic devices of the present invention may be fabricated onother semiconductor substrates as well, including, for example,silicon-on-glass (SOG) substrates, silicon-on-insulator (SOI)substrates, and silicon-on-sapphire (SOS) substrates.

[0098]FIG. 23 is a flow chart of a method 2300 for rapidly propagating arising edge through a skewed logic device in accordance with the presentinvention. Method 2300 includes providing 2302 a skewed logic device.The skewed logic device may be a skewed inverter rising logic device300, a skewed inverter falling logic device 800, a skewed buffer risinglogic device 1400 and a skewed buffer falling logic device 1500, askewed NOR falling logic device 1600, a skewed NOR rising logic device1700, a skewed NAND falling logic device 1800, or skewed NAND risinglogic device 1900, as disclosed herein. Method 2300 further includespropagating 2304 a fast edge through the skewed logic device to anoutput of the skewed logic device and resetting 2306 the output of theskewed logic device.

[0099] Although this invention has been described with reference toparticular embodiments, the invention is not limited to these describedembodiments. Rather, it should be understood that the embodimentsdescribed herein are merely exemplary and that a person skilled in theart may make many variations and modifications without departing fromthe spirit and scope of the invention. All such variations andmodifications are intended to be included within the scope of theinvention as defined in the appended claims.

What is claimed is:
 1. A skewed NOR falling logic device for rapidlypropagating a falling edge of an output signal, comprising: a fast NORgate falling having a large n/p channel width ratio for receiving afirst input signal and a second input signal and rapidly propagating afalling edge of said output signal in response to a rising edge oneither of said first input signal or said second input signal; a pull-upreset network connected in parallel with said fast NOR gate falling forresetting said output signal; and a feedback delay circuit connected inparallel with said pull-up reset network for propagating said outputsignal to an input of said pull-up reset network.
 2. The skewed NORfalling logic device of claim 1, wherein said large n/p channel widthratio ranges from about 5 to about
 200. 3. The skewed NOR falling logicdevice of claim 1, wherein said pull-up reset network comprises:combinational logic having a first input, a second input, a third inputand an output; and a big PMOS transistor having a wide p-channel atleast 10 μm across, a gate node connected to said output of saidcombinational logic, a source node connected to a supply voltage and adrain node connected to said output signal.
 4. The skewed NOR fallinglogic device of claim 3, wherein said combinational logic performs alogical OR function.
 5. The skewed NOR falling logic device of claim 3,wherein said combinational logic comprises: a 3-input NOR gate havingsaid first input connected to said first input signal, having saidsecond input connected to said second input signal and having said thirdinput connected to an output of said feedback delay circuit; and aninverter having an input connected to an output of said 3-input NOR gateand having an output driving said output of said combinational logic. 6.The skewed NOR falling logic device of claim 1, wherein said feedbackdelay circuit comprises four inverters connected in series.
 7. A skewedNAND falling logic device for rapidly propagating a falling edge of anoutput signal, comprising: a fast NAND gate falling having a large n/pchannel width ratio for receiving both a first input signal and a secondinput signal and rapidly propagating a falling edge of said outputsignal in response to rising edges on both said first input signal andsaid second input signal; a pull-up reset network connected in parallelwith said fast NAND gate falling for resetting said output signal aftersaid falling edge of said output signal has been propagated; and afeedback delay circuit connected in parallel with said pull-up resetnetwork for delaying and returning said output signal to an input ofsaid pull-up reset network.
 8. The skewed NAND falling logic device ofclaim 7, wherein said large n/p channel width ratio ranges from about 5to about
 200. 9. The skewed NAND falling logic device of claim 7,wherein said pull-up reset network comprises: combinational logic havinga plurality of inputs and an output; a big PMOS transistor having a widep-channel at least 10 μm across, a gate node connected to said output ofsaid combinational logic, a source node connected to a supply voltageand a drain node connected to said output signal.
 10. The skewed NANDfalling logic device of claim 7, wherein said combinational logicperforms a logical product of sums function.
 11. The skewed NAND fallinglogic device of claim 9, wherein said combinational logic comprises: afirst NOR gate having a first input connected to said first input signaland a second input connected to an output of said feedback delaycircuit; a second NOR gate having a first input connected to said secondinput signal and a second input connected to said output of saidfeedback delay circuit; and a third NOR gate having a first inputconnected to an output of said first NOR gate, a second input connectedto an output of said second NOR gate and an output connected to saidgate node of said big PMOS transistor.
 12. The skewed NAND falling logicdevice of claim 7, wherein said feedback delay circuit comprises fourinverters connected in series.